Typically in the etching of printed circuit boards or other corresponding electronic components or products etching process variations can cause significant deviation of electrical characteristics of the electric circuits between successively etched similar etched circuits. This is especially true when etching high frequency structures such as antenna structures. In the etching of antennas for radio frequency identification tags, RFID tags, for example, the process variations in the etching can cause frequency behaviour variation in the etched antennas, which are typically made of copper or aluminium. In the antennas or in some other, especially high-frequency conductors, the shape and smoothness of edges, especially in curved or corner areas, and the smoothness of the thickness and width of the conductors may have an extensive effect on the frequency or tuning properties of the conductors. An extensive variation in the frequency or tuning properties is not allowable in products like RFID tags to be attached with items sold in department stores, for example, because reading information stored in the tags must happen at a very accurately specified frequency. So, in order to avoid failures or otherwise reduced performance in reading the information stored in the RFID tag, the frequency properties of the antennas in the tags may not essentially vary.
JP-publication 61251035 discloses an arrangement in etching process of wafers. The arrangement comprises a sample electrode and a wafer to be etched located on top of the sample electrode. The arrangement further comprises etchant consuming materials, separate from the wafer and arranged on top of the sample electrode, outside the periphery of the wafer to be etched. The purpose of the usage of the etchant consuming materials is to make the feed rate of the etchant in the surface of the wafer more constant by the working of the etchant consuming materials and in such a way to increase the uniformity of the etching rate on the surface of the wafer to be etched, thereby trying to increase the reproducibility of the etching process of wafers. However, such an arrangement is not enough to ensure good repeatability in etching of items with complicated patterns with significant number of smaller important details.